1/* Copyright (C) 1994-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <bits/types.h>
19
20#ifndef __OFF_T_MATCHES_OFF64_T
21
22#include <unistd.h>
23#include <fcntl.h>
24#include <errno.h>
25
26/* lockf is a simplified interface to fcntl's locking facilities. */
27int
28lockf (int fd, int cmd, off_t len)
29{
30 /* lockf is always relative to the current file position. */
31 struct flock fl = {
32 .l_type = F_WRLCK,
33 .l_whence = SEEK_CUR,
34 .l_len = len
35 };
36
37 /* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
38 used. Therefore we don't have to care about cancellation here,
39 the fcntl() function will take care of it. */
40 switch (cmd)
41 {
42 case F_TEST:
43 /* Test the lock: return 0 if FD is unlocked or locked by this process;
44 return -1, set errno to EACCES, if another process holds the lock. */
45 fl.l_type = F_RDLCK;
46 if (__fcntl (fd, F_GETLK, &fl) < 0)
47 return -1;
48 if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
49 return 0;
50 __set_errno (EACCES);
51 return -1;
52 case F_ULOCK:
53 fl.l_type = F_UNLCK;
54 return __fcntl (fd, F_SETLK, &fl);
55 case F_LOCK:
56 return __fcntl (fd, F_SETLKW, &fl);
57 case F_TLOCK:
58 return __fcntl (fd, F_SETLK, &fl);
59 }
60 __set_errno (EINVAL);
61 return -1;
62}
63#endif
64